The present inventive concept relates to a field emission apparatus, and more particularly, to a field emission apparatus having enhanced focusing capability of an electron beam and improved electron transmission performance.
A field emission apparatus is applicable a variety of devices such as field emission displays, engineering X-ray tubes, and medical X-ray tubes. A performance of the field emission apparatus is essentially affected by controlling characteristics of current density, focusing of field-emitted electron beam, etc. For example, the characteristics of electron beam may be controlled through a material of an emitter or a structure of the field emission apparatus.
A diode-structure field emission apparatus with two electrodes has an anode electrode and a cathode electrode which is attached with an emitter for emitting electrons. Considering a distance between the cathode and anode electrodes, a relatively large voltage is required in a field emission, and this leads to difficulty in controlling the emitted electron beams.
In order to solve the problem, it has been proposed a triode-structure field emission apparatus including three electrodes. The triode-structure field emission apparatus additionally includes a gate electrode as well as the cathode and anode electrode. The triode-structure field emission apparatus uses the gate electrode to control a current magnitude, an electron beam size, focusing of the electron beam, etc.
The gate electrode has a shape having apertures so as to have electron transmission characteristics. It therefore is possible to increase transmission efficiency of electrons from the emitter to the anode electrode. Characteristics of the electron beam are greatly affected by structural features such as size and arrangement of the aperture of the gate electrode. The larger size of the aperture may lead to a higher magnitude of emitted current reaching the anode electrode after passing through the gate electrode. However, the aperture of the gate electrode may induce distortion of potential distribution between the gate electrode and the cathode electrode. Accordingly, a reduced field effect may be applied to the emitter. In addition, the electron beam emitted from the emitter may be distorted in trajectory path. This may result in reducing electron emission of the emitter, in spreading the electron beam, and in decreasing magnitude of the emitted current reaching an effective area of the anode electrode.
Therefore, it is required a field emission apparatus having excellent electron transmission and enhanced focusing capability of the electron beam by reducing potential profile distortion around the aperture.